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Polar Oceans Programme Summary

A CTD (conductivity-temperature-depth) device is retrieved from the Southern Ocean onboard RRS James Clark Ross.
A CTD (conductivity-temperature-depth) device is retrieved from the Southern Ocean onboard RRS James Clark Ross.

Science Leader: Dr Mike Meredith (mmm@bas.ac.uk)

Introduction

Global ocean circulation is one of the few mechanisms by which polar processes can directly influence the whole Earth System, including the UK, and possibly on timescales as short as decades. Its importance results from the enormous capacity of the ocean to store and redistribute heat, fresh water, carbon dioxide and other climatically-important substances. The polar regions are disproportionately important in determining the strength and shape of global ocean circulation.

The Polar Oceans programme investigates the role of processes and changes both in the shelf sea and in open-ocean environments, and will further our understanding of polar control of the Earth System.

Programme Goals

  • To explain the processes that drive and close the overturning circulation in the Southern Ocean
  • To determine the impact of, and the feedback between, the ocean and ice shelves
  • To understand the physical drivers of changes in the marine environment, and the likely implications for climate
  • To determine the impacts that changes in the polar regions have on the Earth System via ocean circulation
  • To measure and understand the changes in properties in key water masses of polar origin

Delivering the Results

Intense atmospheric and cryospheric forcings in the shelf seas around Antarctica lead to the production of the densest waters in the global ocean, while ocean/ice shelf interaction can also affect ice sheet stability. The Polar Oceans programme will deploy oceanographic moorings beneath ice shelves in the Weddell, Amundsen and Bellingshausen Seas using hot water drill technology. The data collected will be combined with science cruise data and phase-sensitive radar measurements of ice shelf basal melt rates, to reveal the nature and extent of interaction between the ocean and the ice shelf in both “cold” and “warm” sectors, and the impacts on the cryosphere and ocean.

The Southern Ocean is filled with small, whirling eddies. These eddies stir the ocean, mixing heat and dissolved chemicals. This figure indicates the amount of mixing generated by these eddies, with regions of strong mixing in red, and weak mixing in blue. (Sea ice concentration is shown in greyscale). The eddies and the mixing they generate also have an important role in modulating the overturning circulation of the entire global ocean.
The Southern Ocean is filled with small, whirling eddies. These eddies stir the ocean, mixing heat and dissolved chemicals. This figure indicates the amount of mixing generated by these eddies, with regions of strong mixing in red, and weak mixing in blue. (Sea ice concentration is shown in greyscale). The eddies and the mixing they generate also have an important role in modulating the overturning circulation of the entire global ocean.

Sustained, high-frequency, oceanographic observations will be continued at the Antarctic Peninsula, as part of the continuing Rothera Time Series programme. Fixed moorings and sediment traps will show how physical processes control the interdisciplinary system in a region of rapid climate change. Sustained measurements using conventional and innovative technologies will allow data collection at times and from regions that are otherwise inaccessible.

The Polar Oceans programme will conduct model-based investigations of shelf-sea circulation and the impacts of the ocean on ice shelves. To understand the impact of the strong wind and buoyancy forcing that drives and closes the overturning circulation in the Southern Ocean, it will analyse the output from existing oceanographic models, and create new, detailed high-resolution oceanographic models. Coupled climate modelling will be used to predict likely future changes in the polar marine environments, and their potential global impacts.

A combination of repeat hydrography and moorings data will measure the export of Antarctic Bottom Water from the Weddell Sea toward the global abyssal ocean, to determine how this varies with time. The Polar Oceans programme will use cruise-based oceanographic data to quantify fluxes of key water masses in the Weddell and Scotia Seas. It will also measure the associated transports of heat, freshwater, and other tracers important for climate.

National and International Context

The Polar Oceans programme will contribute to a number of significant international initiatives, including:

Programme Information

Science Leader:
Dr Michael Meredith (mmm@bas.ac.uk)

Related NERC Science Themes:
Climate System
Earth System Science
Biodiversity

The measurements made will contribute to the interdisciplinary Southern Ocean Observing System (SOOS), and the modelling activities will be used to coordinate SOOS observational plans and data interpretation.

Polar Oceans will enhance the UK’s capability to quantify and understand oceanographic and climatic changes in regions of significant national interest. It will be the primary route for BAS to provide input to its stakeholders on these areas.

The Polar Oceans programme contributes mainly to NERC’s Research Themes on Earth System Science and Climate, particularly the Earth System Science sub-challenges on ocean processes and their interaction with the Earth System, and global biogeochemical cycling; and the Climate challenge to improve understanding of the changing water cycle and how it will affect water availability and quality.

Glossary of terms
Overturning circulation
The global movement of seawater in the ocean. Water sinks to great depth in a few places at high latitudes, spreads horizontally, and rises up toward to the surface in other regions
Repeat hydrography
Vertical profiling of the ocean temperature and salinity that is conducted in the same location repeatedly over extended periods
Antarctic Bottom Water
The cold, dense water mass that forms adjacent to the Antarctic continent, and that flows northward to fill the deepest layer of much of the world’s oceans
Geochemical tracer data
Measurements of the properties of seawater (such as its isotopic composition or substances dissolved in it) that provide information on where the water came from and what processes have influence it
Rothera Time Series
The long time series of oceanographic measurements collected close to Rothera Research Station on the Antarctic Peninsula. See Rothera Time Series webpage